How can we use Twin Research To Identify the
effects of
Sun Ageing and Sun Damage
The Twin Research and Genetic Epidemiology Unit at St Thomas’ Hospital,
London is renowned for have the most widely studied database of twins in the
world. It has nearly 10,000 adult twin volunteers on its books and has studied
everything from obesity and back pain to sense of humour.
The unit has recently focused on the mysteries of the skin and what makes
one individual so different from another, in terms of factors such as skin
ageing and our response to sunlight. Twins are the ideal natural experiment to
separate the effects of nature and nurture. By comparing the similarity of
groups of identical twins (who share all their genes) and non-identical twins
(who share half) the proportion of any trait or characteristic that is due to
genes can be worked out.
Already the Twin Unit under the guidance of Consultant Dermatologist Dr
Veronique Bataille has made some remarkable discoveries into the role of
genes on the skin.
A key research area has been understanding factors which affect ageing of
the skin. For the purpose of our day with Dr Bataille, we have focused in
particular on the effects of sun exposure. The twins have answered a detailed
questionnaire about their sun exposure and use of sunbeds. They also had a
full skin examination performed by trained research nurses.
TWIN RESEARCH HELPS TO CLEARLY IDENTIFY THE LEVEL OF
DAMAGE SUN EXPOSURE CAUSES TO THE SKIN, BY COMPARING
GENETICALLY IDENTICAL INDIVIDUALS, ONE OF WHOM HAS BEEN
MORE EXPOSED TO THE SUN.
Identical twins, who have very different sun exposure histories, show different
features developing from sun exposure. Sun exposed skin is thicker and has
different ultrasound features from skin protected by the sun. It also shows
marked differences skin 'properties' - confirming the role of ultraviolet light in
skin ageing having accounted for genetic differences. The twin skin
programme looks for example at the role of sunlight and sunbeds in
accelerating wrinkles and moles.
The twin skin programme is now looking at the role of sunlight and sunbeds in
accelerating skin ageing, wrinkles and moles – in other words - how our genes
interact with our environment to produce changes in our skin with age. The
reasons for all of us having such different genes that control the way our skin
behaves is slowly becoming clearer.
Understanding the way our skin ages may also give vital clues to why other
parts of our body ages, such as the joints and bones, these age at different
speeds and may also be the clue to longevity.
SUMMARY OF RESEARCH FINDINGS ILLUSTRATED AT THE
WORKSHOP
The tests carried out measure skin thickness on the face, inner and outer arm
(using skin ultrasound), the amount of sebum produced on the forehead
(sebutape test), and also the amount of skin peeling off after applying a sticky
tape (desquame test).
The correlations between identical twins were very high in terms of skin
thickness showing that genes are important: the correlation for sun exposed
sites in identical twins was 0.8 compared to 0.2 in non identical twins.
The following graph shows how similar skin thickness is for twins who share
100% of their genes (identical twins) compared to individuals who only share
50% of their genes (non-identical twins)
Chart 1: Correlations in skin thickness at sun exposed sites in identical
and non-identical twins
0.8
0.7
0.6
0.5
0.4
Correlations
0.3
0.2
0.1
0
Identical twins
Non identical twins
More than 100 pairs of female twins have been studied to compare skin
thickness between sun exposed and non-exposed skin. The skin thickness
on sun-exposed site (outer forearm) was greater than non-sun exposed site
(inner upper arm): 1.18 mm compared to 0,82 mm respectively. Skin
thickness on the forehead the most sun-exposed site was the greatest: 1.6
mm. This represents the disorganisation of the elastic fibres caused by sun
damage.
Chart 1: Skin thickness in mm at different body sites
1.6
1.4
1.2
1
0.8
Thickness
0.6
0.4
0.2
0
Forehead
Outer
forerarm
Inner upper
arm
Refs :
Lister RK, Barnes R, Khorshid M, Cerio R, Tidman N, Bataille V. Structural changes in nonsun-exposed skin of smokers: histological assessment of dermal thickness and elastin. Br J Dermatol
1999;141 (suppl. 55):24
Tran G, Bataille V, Sasieni P, Young M, Dyson M and Spector TD. The influence of genetic and
environmental factors on dermal thickness: a twin study. Br J Dermatol 1998;Suppl
The Twin Unit is still looking for volunteers (both identical and non-identical
twins) to help with its studies. All twins have a health check and full expenses.
Twin Hotline 0207-188-5555 or
website www.twin-research.ac.uk
For further press information please call
Rebecca Filmer at Modus Publicity
on 0207 331 1476
or email rebeccaf@moduspublicity.com